Optical element, and its manufacturing method

ABSTRACT

To provide an optical element including a surface-emitting type semiconductor laser and an photodetector element, having a desired plurality of dielectric layers, and its manufacturing method. An optical element in accordance with the present invention includes a surface-emitting type semiconductor laser including, above a substrate, a first mirror, an active layer and a second mirror disposed from the side of the substrate, a photodetector element, that is provided above the surface-emitting type semiconductor laser, including a first contact layer, a photoabsorption layer and a second contact layer disposed from the side of the surface-emitting type semiconductor laser, a first dielectric layer formed above the substrate, and a second dielectric layer formed above the surface-emitting type semiconductor laser, wherein the first dielectric layer covers a side surface of a first columnar section including at least a portion of the second mirror, and the second dielectric layer covers a side surface of a second columnar section including at least a portion of the second contact layer.

BACKGROUND

The present invention relates to optical elements and methods formanufacturing the same.

A surface-emitting type semiconductor laser has characteristics in whichits light output varies depending on ambient temperatures. For thisreason, there may be cases where an optical module that uses asurface-emitting type semiconductor laser may be equipped with aphotodetector function that detects a part of laser light emitted fromthe surface-emitting type semiconductor laser to thereby monitor lightoutput values. For example, a photodetector element such as a photodiodeor the like may be provided on a surface-emitting type semiconductorlaser, such that a part of laser light emitted from the surface-emittingtype semiconductor laser can be monitored within the same device (forexample, see Patent Document 1).

Patent Document [1] Japanese Laid-open Patent Application HEI 10-135568

SUMMARY

It is an object of the present invention to provide an optical elementincluding a surface-emitting type semiconductor laser and aphotodetector element, having a desired plurality of dielectric layers,and its manufacturing method.

An optical element in accordance with the present invention includes:

a surface-emitting type semiconductor laser including, above asubstrate, a first mirror, an active layer and a second mirror disposedfrom the side of the substrate;

a photodetector element, that is provided above the surface-emittingtype semiconductor laser, including a first contact layer, aphotoabsorption layer and a second contact layer disposed from the sideof the surface-emitting type semiconductor laser;

a first dielectric layer formed above the substrate; and

a second dielectric layer formed above the surface-emitting typesemiconductor laser,

wherein the first dielectric layer covers a side surface of a firstcolumnar section including at least a portion of the second mirror, and

the second dielectric layer covers a side surface of a second columnarsection including at least a portion of the second contact layer.

In an optical element in accordance with the present invention, the casewhere another specific element (hereafter referred to as “B”) is formedabove a specific element (hereafter referred to as “A”), includes a casewhere B is formed directly on A, and a case where B is formed throughanother element above A. This similarly applies to a method formanufacturing an optical element in accordance with the presentinvention.

In the optical element, the first dielectric layer is formed around thefirst columnar section, and the second dielectric layer is formed aroundthe second columnar section. In other words, according to the opticalelement, the desired first dielectric layer and the second dielectriclayer can be disposed in specified regions (regions in a directionperpendicular to the substrate), respectively.

In the optical element in accordance with the present invention, a filmthickness of the first dielectric layer may be thicker than a filmthickness of the second dielectric layer.

In the optical element in accordance with the present invention, thefirst dielectric layer may be composed of a resin, and the seconddielectric layer may be composed of an inorganic dielectric substance.

In the optical element in accordance with the present invention, theresin may be a polyimide resin, an acrylic resin, an epoxy resin, or afluorine resin, and the inorganic dielectric substance may be a siliconnitride or a silicon oxide.

A method for manufacturing an optical element in accordance with thepresent invention pertains to a method for manufacturing an opticalelement including a surface-emitting type semiconductor laser and aphotodetector element, including:

a process of laminating semiconductor layers for forming at least, abovethe substrate, a first mirror, an active layer, a second mirror, a firstcontact layer, a photoabsorption layer and a second contact layer;

a step of forming a first columnar section including at least a portionof the second mirror by etching the semiconductor layers;

a step of forming a second columnar section including at least a portionof the second contact layer by etching the semiconductor layers;

a step of forming a first dielectric layer to cover a side surface ofthe first columnar section; and

a step of forming s second dielectric layer to cover a side surface ofthe second columnar section.

According to the method for manufacturing an optical element, the stepof forming the first dielectric layer and the step of forming the seconddielectric layer are independently conducted. Therefore, an opticalelement having the first dielectric layer and the second dielectriclayer that achieve the aforementioned actions and effects can be formed.

In the method for manufacturing an optical element in accordance withthe present invention, the step of forming the first dielectric layermay include:

a step of forming a precursor layer to cover at least the side surfaceof the first columnar section;

a step of patterning the precursor layer; and

a step of hardening the precursor layer.

In the method for manufacturing an optical element in accordance withthe present invention, the patterning of the precursor layer may beconducted by using a dry etching method or a wet etching method.

In the method for manufacturing an optical element in accordance withthe present invention, the step of forming the second dielectric layermay include:

a step of forming a dielectric layer to cover at least the side surfaceof the second columnar section; and

a step of patterning the dielectric layer.

In the method for manufacturing an optical element in accordance withthe present invention, the dielectric layer may be formed by a plasmaCVD method.

In the method for manufacturing an optical element in accordance withthe present invention, the patterning of the dielectric layer may beconducted by using a dry etching method or a wet etching method.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a cross-sectional view schematically showing an opticalelement in accordance with an embodiment;

FIG. 2 is a cross-sectional view schematically showing an opticalelement in accordance with an embodiment;

FIG. 3 is a cross-sectional view schematically showing an opticalelement in accordance with an embodiment;

FIG. 4 is a cross-sectional view schematically showing a method formanufacturing an optical element in accordance with an embodiment;

FIG. 5 is a cross-sectional view schematically showing the method formanufacturing an optical element in accordance with the embodiment;

FIG. 6 is a cross-sectional view schematically showing the method formanufacturing an optical element in accordance with the embodiment;

FIG. 7 is a cross-sectional view schematically showing the method formanufacturing an optical element in accordance with the embodiment;

FIG. 8 is a cross-sectional view schematically showing the method formanufacturing an optical element in accordance with the embodiment;

FIG. 9 is a cross-sectional view schematically showing the method formanufacturing an optical element in accordance with the embodiment;

FIG. 10 is a cross-sectional view schematically showing the method formanufacturing an optical element in accordance with the embodiment;

FIG. 11 is a cross-sectional view schematically showing the method formanufacturing an optical element in accordance with the embodiment;

FIG. 12 is a cross-sectional view schematically showing the method formanufacturing an optical element in accordance with the embodiment;

FIG. 13 is a cross-sectional view schematically showing the method formanufacturing an optical element in accordance with the embodiment;

FIG. 14 is a cross-sectional view schematically showing an opticalelement in accordance with an embodiment; and

FIG. 15 is a cross-sectional view schematically showing an opticalelement in accordance with an embodiment.

DETAILED DESCRIPTION OF EMBODIMENTS

Preferred embodiments of the present invention are described below withreference to the drawings.

1. Structure of Optical Element

FIG. 1 and FIG. 2 are cross-sectional views schematically showing anoptical element 100 in accordance with an embodiment of the presentinvention. Also, FIG. 3 is a plan view schematically showing the opticalelement 100 shown in FIG. 1 and FIG. 2. It is noted that FIG. 1 is aview indicating a cross section taken along a line A-A in FIG. 3, andFIG. 2 is a view indicating a cross section taken along a line B-B inFIG. 3.

The optical element 100 in accordance with the present embodiment, asshown in FIG. 1, includes a surface-emitting type semiconductor laser140, a first dielectric layer 30, an isolation layer 20, a photodetectorelement 120, and a second dielectric layer 40.

The surface-emitting type semiconductor laser 140, the first dielectriclayer 30, the isolation layer 20, the photodetector element 120, thesecond dielectric layer 40, and an overall structure are describedbelow.

1-1. Surface-Emitting Type Semiconductor Laser

The surface-emitting type semiconductor laser 140 is provided on asemiconductor substrate (an n-type GaAs substrate in the presentembodiment) 101. The surface-emitting type semiconductor laser 140includes a vertical resonator. Also, the surface-emitting typesemiconductor laser 140 can include a columnar semiconductor depositionbody (hereafter referred to as a “columnar section”) 130.

The surface-emitting type semiconductor laser 140 is formed from, forexample, a distributed reflection type multilayer mirror of 40 pairs ofalternately laminated n-type Al_(0.9)Ga_(0.1)As layers and n-typeAl_(0.15) Ga_(0.85)As layers (hereafter called a “first mirror”) 102, anactive layer 103 composed of GaAs well layers and Al_(0.3)Ga_(0.7)Asbarrier layers in which the well layers include a quantum well structurecomposed of three layers, and a distributed reflection type multilayermirror of 25 pairs of alternately laminated p-type Al_(0.9)Ga_(0.1)Aslayers and p-type Al_(0.15)Ga_(0.85)As layers (hereafter called a“second mirror”) 104, which are successively stacked in layers. It isnoted that an uppermost layer 14 of the second mirror 104 is composed tobe a layer with a small Al composition, in other words, a p-typeAl_(0.15)Ga_(0.85)As layer.

In the present embodiment, the Al composition of an AlGaAs layer is acomposition of aluminum (Al) to gallium (Ga). The Al composition in anAlGaAs layer is from 0 to 1. In other words, an AlGaAs layer includes aGaAs layer (when the Al composition is 0) and an AlAs layer (when the Alcomposition is 1).

The composition of each of the layers and the number of the layersforming the first mirror 102, the active layer 103 and the second mirror104 are not particularly limited to the above. It is noted that the Alcomposition of the uppermost layer 14 of the second mirror 104 maypreferably be less than 0.3. The reason for this is described below.

The second mirror 104 is formed to be p-type by, for example, dopingcarbon (C), and the first mirror 102 is formed to be n-type by, forexample, doping silicon (Si). Accordingly, the p-type second mirror 104,the active layer 103 in which no impurity is doped, and the n-type firstmirror 102 form a pin diode.

A portion among the surface-emitting type semiconductor laser 140extending from the second mirror 104 to an intermediate point of thefirst mirror 102 is etched in a circular shape, as viewed from an uppersurface 104 a of the second mirror 104, thereby forming a columnarportion 130. It is noted that, in the present embodiment, the columnarportion 130 has a plane configuration that is circular, but itsconfiguration can have any arbitrary configuration.

Furthermore, a current constricting layer 105, that is obtained byoxidizing the AlGaAs layer from its side surface, is formed in a regionnear the active layer 103 among layers composing the second mirror 104.The current constricting layer 105 is formed in a ring shape. In otherwords, the current constricting layer 105 has a cross section, when cutin a plane parallel with a surface 101 a of the semiconductor substrate101 shown in FIG. 1 and FIG. 2, which is a circular ring shapeconcentric with a circle of the plane configuration of the columnarsection 130.

Also, the surface-emitting type semiconductor laser 140 is provided witha first electrode 107 and a second electrode 109. The first electrode107 and the second electrode 109 are used to drive the surface-emittingtype semiconductor laser 140.

More specifically, as shown in FIG. 1, the first electrode 107 isprovided on an upper surface 102 a of the first mirror 102. The firstelectrode 107, as shown in FIG. 3, has a plane configuration of a ringshape. In other words, the first electrode 107 is provided in a mannerto surround mainly the columnar section 130. Stated otherwise, thecolumnar section 130 is provided inside the first electrode 107.

The second electrode 109 is provided on an upper surface 104 a of thesurface-emitting type semiconductor laser 140. The second electrode 109,as shown in FIG. 3, has a connection section 109 a having a planeconfiguration of a ring shape, a leading section 109 b having a planeconfiguration of a linear shape, and a pad section 109 c having acircular plane configuration. The second electrode 109 is electricallyconnected to the second mirror 104 at the connection section 109 a. Theleading section 109 b of the second electrode 109 connects theconnection section 109 a and the pad section 109 c. The pad section 109c of the second electrode can be used as an electrode pad. Theconnection section 109 a of the second electrode 109 is provided in amanner to surround mainly an isolation layer 20 to be described below.In other words, the isolation layer 20 is provided inside the secondelectrode 109.

It is noted that, although the present embodiment indicates a case wherethe first electrode 107 is provided on the first mirror 102, the firstelectrode 107 can be provided on a back surface 101 b of thesemiconductor substrate 101.

The first electrode 107 is composed of a laminated film of an alloy ofgold (Au) and germanium (Ge), and gold (Au), for example. The secondelectrode 109 is composed of a laminated film of platinum (Pt), titanium(Ti) and gold (Au), for example. Electric current is injected in theactive layer 103 by the first electrode 107 and the second electrode109. It is noted that the materials for forming the first electrode 107and the second electrode 109 are not limited to those described above,but, for example, an alloy of gold (Au) and zinc (Zn) can be used.

1-2. First Dielectric Layer

In the optical element in accordance with the present embodiment, afirst dielectric layer 30 is formed in a manner to surround mainly thecolumnar section 130. The first dielectric layer 30 is formed on thefirst mirror 102. Further, the first dielectric layer 30 is formed belowa leading section 109 b and a pad section 109 c of a second electrode109 to be described below. Moreover, the first dielectric layer 30 isformed below a second dielectric layer 40 to be described below.

1-3. Isolation Layer

In the optical element 100 of the present embodiment, the isolationlayer 20 is formed on the surface-emitting type semiconductor laser 140.In other words, the isolation layer 20 is provided between thesurface-emitting type semiconductor laser 140 and a photodetectorelement 120 to be described below. More specifically, as shown in FIG. 1and FIG. 2, the isolation layer 20 is formed on the second mirror 104.Namely, the isolation layer 20 is provided between the second mirror 104and a first contact layer 111 to be described below.

The isolation layer 20 has a circular plane configuration. In theillustrated example, the plane configuration of the isolation layer 20is the same as the plane configuration of the first contact layer 111.The plane configuration of the isolation layer 20 can be formed to belarger than the plane configuration of the first contact layer 111. Theisolation layer 20 will be described in greater detail in conjunctionwith a method for manufacturing an optical element to be describedbelow.

1-4. Photodetector Element

The photodetector element 120 is provided on the isolation layer 20. Inthe optical element 100 of the present embodiment, the upper surface ofthe photodetector element 120 includes an emission surface 108 of laserlight.

Also, the photodetector element 120 includes the first contact layer111, a photoabsorption layer 112, and a second contact layer 113. Thefirst contact layer 111 is provided on the isolation layer 20, thephotoabsorption layer 112 is provided on the first contact layer 111,and the second contact layer 113 is provided on the photoabsorptionlayer 112. The first contact layer 111 has a plane configuration that isformed to be larger than the plane configuration of either thephotoabsorption layer 112 or the second contact layer 113 (see FIG. 1and FIG. 2). The second contact layer 113 and the photoabsorption layer112 compose a columnar semiconductor stacked body (hereafter referred toas a “second columnar section”) 132.

The first contact layer 111 may be composed of, for example, an n-typeGaAs layer, the photoabsorption layer 112 may be composed of, forexample, a GaAs layer with no impurity being introduced, and the secondcontact layer 113 may be composed of, for example, a p-type GaAs layer.More specifically, the first contact layer 111 is made to be n-type bydoping, for example, silicon (Si), and the second contact layer 113 ismade to be p-type by doping, for example, carbon (C). Accordingly, then-type first contact layer 111, the photoabsorption layer 112 without animpurity being doped, and the p-type second contact layer 113 form a pindiode.

The photodetector element 120 is provided with a third electrode 116 anda fourth electrode 110. The third electrode 116 and the fourth electrode110 are used to drive the photodetector element 120. More specifically,as shown in FIG. 1 and FIG. 2, the third electrode 116 is formed in amanner to cover the first contact layer 111. A part of the thirdelectrode 116 is formed on the above-described second electrode 109. Inother words, the third electrode 116 and the second electrode 109 areelectrically connected. As shown in FIG. 3, the third electrode 116 hasa plane configuration of a ring shape. Namely, the third electrode 116is provided in a manner to surround mainly the first contact layer 111and the second dielectric layer 40. Stated otherwise, the first contactlayer 111 and the second dielectric layer 40 are provided inside thethird electrode 116.

The fourth electrode 110 has, as shown in FIG. 3, a connection section110 a having a plane configuration of a ring shape, a leading section110 b having a plane configuration of a linear shape, and a pad section110 c having a circular plane configuration. The fourth electrode 110 iselectrically connected to the second contact layer 113 at the connectionsection 110 a. The leading section 110 b of the fourth electrode 110connects the connection section 110 a and the pad section 110 c. The padsection 110 c of the fourth electrode can be used as an electrode pad.The fourth electrode 110 is provided on an upper surface (on the secondcontact layer 113) of the photodetector element 120. The fourthelectrode 110 is provided with an aperture section 114, and a part of anupper surface of the second contact layer 113 is exposed through theaperture section 114. The exposed surface is the emission surface 108 oflaser light. Accordingly, by appropriately setting the planeconfiguration and the size of the opening section 114, the configurationand the size of the emission surface 108 can be appropriately set. Inthe present embodiment, as shown in FIG. 3, a case in which the emissionsurface 108 is in a circular shape is indicated.

Also, in the optical element 100 in accordance with the presentembodiment, the third electrode 116 can be formed with the same materialas that of the first electrode 107, and the fourth electrode 110 can beformed with the same material as that of the second electrode 109.

1-5. Second Dielectric Layer

In the optical element 100 in accordance with the present embodiment, asecond dielectric layer 40 is formed in a manner to surround mainly thesecond columnar section 132. The second dielectric layer 40, as shown inFIG. 1-FIG. 3, is formed over the first contact layer 111, the secondmirror 104 and the first dielectric layer 30. Furthermore, the seconddielectric layer 40 is formed below the leading section 110 b and thepad section 110 c of the fourth electrode 110.

1-6. Overall Structure

In the optical element 100 in accordance with the present embodiment,the n-type first mirror 102 and the p-type second mirror 104 of thesurface-emitting type semiconductor laser 140, and the n-type firstcontact layer 111 and the p-type second contact layer 113 of thephotodetector element 120 form a npnp structure as a whole.

The photodetector element 120 has a function to monitor outputs of lightgenerated by the surface-emitting type semiconductor laser 140. Morespecifically, the photodetector element 120 converts light generated bythe surface-emitting type semiconductor laser 140 into electric current.With values of the electric current, outputs of light generated by thesurface-emitting type semiconductor laser 140 can be detected.

More specifically, in the photodetector element 120, a part of lightgenerated by the surface-emitting type semiconductor laser 140 isabsorbed by the photoabsorption layer 112, and photoexcitation is causedby the absorbed light in the photoabsorption layer 112, and electronsand holes are generated. Then, by an electric field that is applied froman outside element, the electrons move to the third electrode 116 andthe holes move to the fourth electrode 110, respectively. As a result, acurrent is generated in the direction from the first contact layer 111to the second contact layer 113 in the photodetector element 120.

Also, light output of the surface-emitting type semiconductor laser 140is determined mainly by a bias voltage applied to the surface-emittingtype semiconductor laser 140. In particular, light output of thesurface-emitting type semiconductor laser 140 greatly changes dependingon the ambient temperature of the surface-emitting type semiconductorlaser 140 and the service life of the surface-emitting typesemiconductor laser 140. For this reason, it is necessary for thesurface-emitting type semiconductor laser 140 to maintain apredetermined level of light output.

In the optical element 100 in accordance with the present embodiment,light output of the surface-emitting type semiconductor laser 140 ismonitored, and the value of a voltage to be applied to thesurface-emitting type semiconductor laser 140 is adjusted based on thevalue of a current generated by the photodetector element 120, wherebythe value of a current flowing within the surface-emitting typesemiconductor laser 140 can be adjusted. Accordingly, a predeterminedlevel of light output can be maintained in the surface-emitting typesemiconductor laser 140. The control to feed back the light output ofthe surface-emitting type semiconductor laser 140 to the value of avoltage to be applied to the surface-emitting type semiconductor laser140 can be performed by using an external electronic circuit (a drivecircuit not shown).

2. Operation of Optical Element

General operations of the optical element 100 of the present embodimentare described below. It is noted that the following method for drivingthe optical element 100 is described as an example, and various changescan be made without departing from the subject matter of the presentinvention.

When a voltage in a forward direction is applied to the pin diode acrossthe first electrode 107 and the second electrode 109, recombination ofelectrons and holes occur in the active layer 103 of thesurface-emitting type semiconductor laser 140, thereby causing emissionof light due to the recombination. Stimulated emission occurs during theperiod the generated light reciprocates between the second mirror 104and the first mirror 102, whereby the light intensity is amplified. Whenthe optical gain exceeds the optical loss, laser oscillation occurs,whereby laser light is emitted from the upper surface 104 a of thesecond mirror 104, and enters the isolation layer 20. Next, the laserlight enters the first contact layer 111 of the photodetector element120.

Then, in the photodetector element 120, the light entered the firstcontact layer 111 then enters the photoabsorption layer 112. As a resultof a part of the incident light being absorbed by the photoabsorptionlayer 112, photoexcitation is caused in the photoabsorption layer 112,and electrons and holes are generated. Then, by an electric field thatis applied from an outside element, the electrons move to the thirdelectrode 116 and the holes move to the fourth electrode 110,respectively. As a result, a current (photoelectric current) isgenerated in the direction from the first contact layer 111 to thesecond contact layer 113 in the photodetector element 120. By measuringthe value of the current, light output of the surface-emitting typesemiconductor laser 140 can be detected.

3. Method for Manufacturing Optical Element

Next, one example of a method for manufacturing the optical element 100in accordance with an embodiment of the present invention is described,using FIG. 4-FIG. 13. FIG. 4-FIG. 13 are cross-sectional viewsschematically showing a process of manufacturing the optical element 100shown in FIG. 1-FIG. 3, and correspond to the cross-sectional view shownin FIG. 1, respectively.

(1) First, on a surface 101 a of a semiconductor substrate 101 composedof an n-type GaAs layer, a semiconductor multilayer film 150 shown inFIG. 4 is formed by epitaxial growth while modifying its composition. Itis noted here that the semiconductor multilayer film 150 is formed from,for example, a first mirror 102 of 40 pairs of alternately laminatedn-type Al_(0.9)Ga_(0.1)As layers and n-type Al_(0.15)Ga_(0.85)As layers,an active layer 103 composed of GaAs well layers and Al_(0.3)Ga_(0.7)Asbarrier layers in which the well layers include a quantum well structurecomposed of three layers, a second mirror 104 of 25 pairs of alternatelylaminated p-type Al_(0.9)Ga_(0.1)As layers and p-typeAl_(0.15)Ga_(0.85)As layers, an isolation layer 20 composed of an AlGaAslayer without impurities being doped, a first contact layer 111 composedof an n-type GaAs layer, a photoabsorption layer 112 composed of a GaAslayer without impurities being doped, and a second contact layer 113composed of a p-type GaAs layer. These layers are successively stackedin layers on the semiconductor substrate 101, thereby forming thesemiconductor multilayer film 150. It is noted that the isolation layer20 can be composed of a p-type or n-type AlGaAs layer.

The isolation layer 20 whose etching rate to a second etchant to bedescribed below is greater than an etching rate of an uppermost layer 14of the second mirror 104 to the second etchant can be used. Morespecifically, for example, the isolation layer 20 can be composed of anAlGaAs layer having an Al composition that is greater than an Alcomposition of the uppermost layer 14 of the second mirror 104. In otherwords, when the second mirror 104 is grown, the uppermost layer 14 ofthe second mirror 104 is formed to become an AlGaAs layer having an Alcomposition smaller than the Al composition of the isolation layer 20.More specifically, the uppermost layer 14 of the second mirror 104 andthe isolation layer 20 may preferably be formed such that the Alcomposition of the uppermost layer 14 of the second mirror 104 is lessthan 0.3, and the Al composition of the isolation layer 20 is 0.3 orgreater.

The isolation layer 20 whose etching rate to a first etchant to bedescribed below is smaller than an etching rate of the first contactlayer 111 to the first etchant can be used. More specifically, forexample, the isolation layer 20 can be composed of an AlGaAs layerhaving an Al composition that is greater than an Al composition of thefirst contact layer 111. In other words, when the first contact layer111 is grown, the first contact layer 111 is formed to become an AlGaAslayer (including a GaAs layer) having an Al composition smaller than theAl composition of the isolation layer. More specifically, the firstcontact layer 111 and the isolation layer 20 may preferably be formedsuch that the Al composition of the first contact layer 111 is less than0.3, and the Al composition of the isolation layer 20 is 0.3 or greater.

It is noted that, when the second mirror 104 is grown, at least onelayer thereof near the active layer 103 is formed to be a layer that islater oxidized and becomes a current constricting layer 105 (see FIG.9). More specifically, the layer that becomes the current constrictinglayer 105 is formed to be an AlGaAs layer (including an AlAs layer)having an Al composition that is greater than an Al composition of theisolation layer 20. In other words, the isolation layer 20 can be formedto be an AlGaAs layer whose Al composition is smaller than that of thelayer that becomes to be the current constricting layer 105. By this, inan oxidizing process (see FIG. 9) for forming the current constrictinglayer 105 to be described below, the isolation layer 20 cannot beoxidized. More specifically, the layer that becomes to be the currentconstricting layer 105 and the isolation layer 20 may preferably beformed such that the Al composition of the layer that becomes to be thecurrent constricting layer 105 is 0.95 or greater, and the Alcomposition of the isolation layer 20 is less than 0.95.

An optical film thickness of the isolation layer 20 can be, for example,an odd multiple of λ/4, when a design wavelength of the surface-emittingtype semiconductor laser 140 (see FIG. 1 and FIG. 2) is λ.

Also, the sum of optical film thickness of the first contact layer 111,the photoabsorption layer 112 and the second contact layer 113, in otherwords, the optical film thickness of the entire photodetector element120 (see FIG. 1 and FIG. 2), can be, for example, an odd multiple ofλ/4. As a result, the entire photodetector element 120 can function as adistributed reflection type mirror. In other words, the entirephotodetector element 120 can function as a distributed reflection typemirror above the active layer 103 in the surface-emitting typesemiconductor laser 140. Accordingly, the photodetector element 120 canfunction as a distributed reflection type mirror without adverselyaffecting the characteristics of the surface-emitting type semiconductorlaser 140.

Also, when a second electrode 109 is formed in a later step, at least aportion of the second mirror 104 near an area contacting the secondelectrode 109 may preferably be formed with a high carrier density suchthat ohmic contact can be readily made with the second electrode 109.Similarly, at least a portion of the first contact layer 111 near anarea contacting the third electrode 116 may preferably be formed with ahigh carrier density such that ohmic contact can be readily made withthe third electrode 116.

The temperature at which the epitaxial growth is conducted isappropriately decided depending on the growth method, the kind of rawmaterial, the type of the semiconductor substrate 101, and the kind,thickness and carrier density of the semiconductor multilayer film 150to be formed, and in general may preferably be 450° C.-800° C. Also, thetime required for conducting the epitaxial growth is appropriatelydecided like the temperature. Also, a metal-organic chemical vapordeposition (MOVPE: Metal-Organic Vapor Phase Epitaxy) method, a MBEmethod (Molecular Beam Epitaxy) method or a LPE (Liquid Phase Epitaxy)method can be used as a method for the epitaxial growth.

(2) Next, a second columnar section 132 is formed (see FIG. 5).

First, resist (not shown) is coated on the semiconductor multilayer film150, and then the resist is patterned by a lithography method, therebyforming a resist layer R1 having a specified pattern.

Then, by using the resist layer R1 as a mask, the second contact layer113 and the photoabsorption layer 112 are etched by, for example, a dryetching method. By this, the second contact layer 113 and thephotoabsorption layer 112 having the same plane configuration as that ofthe second contact layer 113 are formed. In other words, the secondcolumnar section 132 is formed. Then, the resist layer R1 is removed.

(3) Then, the first contact layer 111 is patterned into a specifiedpattern (see FIG. 6). More specifically, first, resist (not shown) iscoated on the first contact layer 111, and then the resist is patternedby a lithography method, thereby forming a resist layer R2 having aspecified pattern.

Then, by using the resist layer R2 as a mask, the first contact layer111 is etched with a first etchant. In this instance, because theisolation layer 20 is disposed below the first contact layer 111, andthe isolation layer 20 functions as an etching stopper layer, etching ofthe first contact layer 111 can be accurately and readily stopped at thetime when the isolation layer 20 is exposed. More specifically, thefollowing is conducted.

As described above, the isolation layer 20 having an etching rate to thefirst etchant that is smaller than an etching rate of the first contactlayer 111 to the first etchant can be used. In other words, initially,the first contact layer 111 is etched at a greater etching rate untilthe isolation layer 20 is exposed. Then, the isolation layer 20 isexposed.

The etching rate of the isolation layer 20 is smaller than the etchingrate of the first contact layer 111. In other words, the isolation layer20 is more difficult to be etched compared to the first contact layer111. Accordingly, at the time when the isolation layer 20 is exposed,etching with the first etchant becomes difficult to take place, andtherefore it is easy to stop etching at this point of time. In otherwords, etching of the first contact layer 111 can be accurately andreadily stopped at the time when the isolation layer 20 is exposed.

More specifically, for example, the isolation layer 20 can be composedof an AlGaAs layer having an Al composition greater than the Alcomposition of the first contact layer 111. Then, the first etchant canbe selected such that the etching rate of the AlGaAs layer having alarge Al composition is small, and the etching rate of the AlGaAs layerhaving a small Al composition is large. In other words, the firstetchant that selectively etches the AlGaAs layer having a small Alcomposition can be selected. By this, the etching rate of the isolationlayer 20 to the first etchant can be made smaller than the etching rateof the first contact layer 111 to the first etchant.

As described above, the Al composition of the isolation layer 20 ispreferably 0.3 or greater, and the Al composition of the first contactlayer 111 is preferably less than 0.3. In this case, a mixed solution ofammonia, hydrogen peroxide and water can be used as the first etchant.For example, the mixing ratio of ammonia, hydrogen peroxide and waterthat is about 1:10:150 can be used, but this mixing ratio is notparticularly limited, and can be appropriately decided.

As a result, as shown in FIG. 6, the photodetector element 120 isformed. The photodetector element 120 includes the second contact layer113, the photoabsorption layer 112 and the first contact layer 111.Also, the plane configuration of the first contact layer 111 may beformed to be greater than the plane configuration of the second contactlayer 113 and the photoabsorption layer 112.

In the process described above, the case where after the second contactlayer 111 and the photoabsorption layer 112 are patterned, the firstcontact layer 111 is patterned is described. However, after the firstcontact layer 111 may be patterned, and then the second contact layer111 and the photoabsorption layer 112 may be patterned.

(4) Next, the isolation layer 20 is patterned into a specified pattern(see FIG. 7). More specifically, using the aforementioned resist R2 as amask, the isolation layer 20 is etched with a second etchant. In thisinstance, because the uppermost layer 14 of the second mirror 104 isdisposed below the isolation layer 20, and the uppermost layer 14 of thesecond mirror 104 functions as an etching stopper layer, etching of theisolation layer 20 can be accurately and readily stopped at the timewhen the uppermost layer 14 of the second mirror 104 is exposed. Morespecifically, the following is conducted.

As described above, the isolation layer 20 having an etching rate to thesecond etchant that is greater than an etching rate of the uppermostlayer 14 of the second mirror 104 to the second etchant can be used. Inother words, initially, the isolation layer 20 is etched at a greateretching rate until the uppermost layer 14 of the second mirror 104 isexposed. Then, the uppermost layer 14 of the second mirror 104 isexposed.

The etching rate of the uppermost layer 14 of the second mirror 104 issmaller than the etching rate of the isolation layer 20. In other words,the uppermost layer 14 of the second mirror 104 is more difficult to beetched compared to the isolation layer 20. Accordingly, at the time whenthe uppermost layer 14 of the second mirror 104 is exposed, etching withthe second etchant becomes difficult to take place, and therefore it iseasy to stop etching at this point of time. In other words, etching ofthe isolation layer 20 can be accurately and readily stopped at the timewhen the uppermost layer 14 of the second mirror 104 is exposed.

More specifically, for example, the isolation layer 20 can be composedof an AlGaAs layer having an Al composition greater than the Alcomposition of the uppermost layer 14 of the second mirror 104. Then,the second etchant can be selected such that the etching rate of theAlGaAs layer having a large Al composition is large, and the etchingrate of the AlGaAs layer having a small Al composition is small. Inother words, the second etchant that selectively etches the AlGaAs layerhaving a large Al composition can be selected. By this, the etching rateof the isolation layer 20 to the second etchant can be made greater thanthe etching rate of the uppermost layer 14 of the second mirror 104 tothe second etchant.

As described above, the Al composition of the isolation layer 20 ispreferably 0.3 or greater, and the Al composition of the uppermost layer14 of the second mirror 104 is preferably less than 0.3. In this case,for example, hydrofluoric acid can be used as the second etchant. Theconcentration of the hydrofluoric acid may be about 0.1%, for example,but the concentration of the hydrofluoric acid is not particularlylimited, and can be appropriately decided.

As a result, as shown in FIG. 7, the isolation layer 20 that ispatterned is formed. Then, the resist layer R2 is removed. In theillustrated example, the plane configuration of the isolation layer 20is formed to be the same as the plane configuration of the first contactlayer 111. But the plane configuration of the isolation layer 20 can beformed to be greater than the plane configuration of the first contactlayer 111. More specifically, instead of the resist layer R2 that isused for patterning the isolation layer 20 described above, anotherresist layer having a plane configuration greater than that of theresist layer R2 may be used to pattern the isolation layer 20.

(5) Next, by patterning, a surface-emitting type semiconductor laser 140including a first columnar section 130 is formed (see FIG. 8). Morespecifically, first, resist (not shown) is coated on the second mirror104, and then the resist is patterned by a lithography method, therebyforming a resist layer R3 having a specified pattern. Then, by using theresist layer R3 as a mask, the second mirror 104, the active layer 103and a part of the first mirror 102 are etched by, for example, a dryetching method. By this, as shown in FIG. 8, the first columnar section130 is formed.

By the process described above, a vertical resonator including the firstcolumnar section 130 (surface-emitting type semiconductor laser 140) isformed on the semiconductor substrate 101. In other words, a laminatedbody of the surface-emitting type semiconductor laser 140, the isolationlayer 20 and the photodetector element 120 is formed. Then, the resistlayer R3 is removed.

In the present embodiment, as described above, the case where thephotodetector element 120 and the isolation layer 20 are first formed,and then the first columnar section 130 is formed is described. However,the first columnar section 130 may be formed first, and then thephotodetector element 120 and the isolation layer 20 may be formed.

Next, by placing the semiconductor substrate 101 on which the firstcolumnar section 130 is formed through the aforementioned steps in awater vapor atmosphere at about 400° C., for example, a layer having ahigh Al composition provided in the second mirror 104 is oxidized fromits side surface, thereby forming a current constricting layer 105 (seeFIG. 9). As described above, in this step, it is possible that theisolation layer 20 is not oxidized.

The oxidation rate depends on the temperature of the furnace, the amountof water vapor supply, and the Al composition and the film thickness ofthe layer to be oxidized. In a surface-emitting type laser equipped witha current constricting layer that is formed by oxidation, a currentflows only in a portion where the current constricting layer is notformed (a portion that is not oxidized). Accordingly, in the process forforming the current constricting layer by oxidation, the range of thecurrent constricting layer 105 to be formed may be controlled, wherebythe current density can be controlled.

Also, the diameter of the current constricting layer 105 may preferablybe adjusted such that a major portion of light that is emitted from thesurface-emitting type semiconductor laser 140 enters the first contactlayer 111.

(7) Next, as shown in FIG. 10, a first dielectric layer 30 is formed onthe first mirror 102, around the columnar section 130. The firstdielectric layer 30 may use material that is easier to make a thick filmcompared to a second dielectric layer 40. The film thickness of thefirst dielectric layer 30 may be about 2-4 μm, for example, but it isnot particularly limited, and can be a film thickness thicker than thefilm thickness of the second dielectric layer 40. For example, the firstdielectric layer 30 can use material that is obtained by hardeningliquid material settable by energy, such as, heat, light or the like(for example, a precursor of ultraviolet setting type resin orthermosetting type resin). As the ultraviolet setting type resin, forexample, an acrylic resin, an epoxy resin or the like that is anultraviolet setting type can be enumerated. Also, as the thermosettingtype resin, a polyimide resin or the like that is a thermosetting typecan be enumerated. Also, for example, the first dielectric layer 30 canbe made to be a laminated film using a plurality of the materialsdescribed above.

Here, the case where a precursor of polyimide resin is used as thematerial for forming the first dielectric layer 30 is described. First,for example, by using a spin coat method, the precursor (precursor ofpolyimide resin) is coated on the semiconductor substrate 101, therebyforming a precursor layer. It is noted that, as the method for formingthe precursor layer, besides the aforementioned spin coat method,another known technique, such as, a dipping method, a spray coat method,an ink jet method or the like can be used.

Then, the semiconductor substrate 101 is heated by using, for example, ahot plate or the like, thereby removing the solvent, and then is placedin a furnace at about 350° C. to thereby imidize the precursor layer,thereby forming a polyimide resin layer that is almost perfectly set.Then, as shown in FIG. 10, the polyimide resin layer is patterned byusing a known lithography technique, thereby forming the firstdielectric layer 30. As the etching method used for patterning, a dryetching method or the like can be used. Dry etching can be conductedwith, for example, oxygen or argon plasma.

In the method for forming the first dielectric layer 30 described above,an example is presented in which a precursor layer of polyimide resin isset, and then patterning is conducted. However, patterning may beconducted before the precursor layer of polyimide resin is set. As theetching method used for this patterning, a wet etching method or thelike can be used. The wet etching can be conducted with, for example, analkaline solution or an organic solution.

(8) Next, as shown in FIG. 11, a second dielectric layer 40 is formed onthe first contact layer 111, around the second columnar section 132. Thesecond dielectric layer 40 can use material that is easy to performmicro processing compared with the first dielectric layer 30. The filmthickness of the second dielectric layer 40 may be about 0.1-0.5 μm, forexample, but it is not particularly limited, and can be a film thicknessthat is thinner than the film thickness of the first dielectric layer30. For example, as the second dielectric layer 40, an inorganicdielectric film such as a silicon oxide film, a silicon nitride film, ora laminated film of them can be used. Specifically, the method forforming the second dielectric layer 40 is conducted as follows.

First, a dielectric layer (not shown) is formed over the entire surfaceof the semiconductor substrate 101 on which the surface-emitting typesemiconductor laser 140 and the photodetector element 120 are formed.This dielectric layer can be formed by, for example, a plasma CVD. Next,by using a known lithography technique, the dielectric layer ispatterned, thereby forming a second dielectric layer 40. The seconddielectric layer 40 can be patterned more finely compared to the firstdielectric layer 30 as described above. As the etching method used forthis patterning, a dry etching method or a wet etching method can beused. The dry etching can be conducted with plasma including fluorineradical, for example. The wet etching can be conducted with hydrofluoricacid, for example.

(9) Then, a second electrode 109 is formed on an upper surface 104 a ofthe second mirror 104, and a fourth electrode 110 is formed on an uppersurface of the photodetector element 120 (an upper surface 113 a of thesecond contact layer 113) (see FIG. 12).

First, before the second electrode 109 and the fourth electrode 110 areformed, the upper surface 104 a of the second mirror 104 and the uppersurface 113 a of the second contact layer 113 are washed by using aplasma processing method or the like, depending on the necessity. As aresult, an element with more stable characteristics can be formed.

Next, a laminated film (not shown) of platinum (Pt), titanium (Ti), andgold (Au), for example, is formed by, for example, a vacuum depositionmethod. Then, the second electrode 109 and the fourth electrode 110 areformed by removing the laminated film other than specified positions bya lift-off method. In this instance, a portion where the above-mentionedlaminated film is not formed is formed on the upper surface 113 a of thesecond contact layer 113. This portion becomes an opening section 114,and a portion of the upper surface 113 a of the second contact layer 113is exposed through the opening section 114. The exposed surface becomesan emission surface 108 of laser light.

As described above, the second electrode 109 can include at leastplatinum (Pt). The second electrode 109 can use an alloy of gold (Au)and zinc (Zn), for example. Most preferably, the second electrode 109includes platinum. The reason is as follows.

It the optical element 100 in accordance with the present embodiment,the second electrode 109 contacts the p-type second mirror 104 (see FIG.1 and FIG. 2). If the second electrode 109 includes zinc (Zn), it ispossible that zinc may diffuse in the p-type second mirror 104 in ananneal processing step to be described below, since zinc thermallydiffuses in an amount greater than that of platinum, and may reach theadjacent n-type first contact layer 111. Because zinc is a p-type dopantin the first contact layer 111 that is composed of a GaAs layer, it maychange the n-type first contact layer 111 to p-type. As a result, thepin structure in the photodetector element 120 may be destroyed. Incontrast, platinum has a smaller thermal diffusion amount compared tozinc, and therefore the n-type first contact layer 111 can be preventedfrom being changed to p-type.

It is noted that a dry etching method or a wet etching method can beused in the above-described process instead of the lift-off method.Also, in the process described above, a sputter method can be usedinstead of the vapor deposition method. Further, in the processdescribed above, although the second electrode 109 and the fourthelectrode 110 are patterned at the same time, the second electrode 109and the fourth electrode 110 can be formed individually.

(10) Next, by a similar method, a laminated film of an alloy of gold(Au) and germanium (Ge), and gold (Au) is patterned, whereby a firstelectrode 107 is formed on the first mirror 102 of the surface-emittingtype semiconductor laser 140, and a third electrode 116 is formed on thefirst contact layer 111 of the photodetector element 120 (see FIG. 13).The first electrode 107 and the third electrode 116 can be patterned andformed at the same time, or the first electrode 107 and the thirdelectrode 116 may be formed individually.

(11) Next, an annealing treatment is conducted. The temperature of theannealing treatment depends on the electrode material. This is usuallyconducted at about 400° C. for the electrode material used in thepresent embodiment. The first-fourth electrodes 107, 109, 110, 116 areformed with the process described above.

By the process described above, as indicated in FIG. 1-FIG. 3, theoptical element 100 in accordance with the present embodiment can beobtained.

4. Actions and Effects

The optical element 100 and its manufacturing method in accordance withthe present embodiment have actions and effects as follows.

According to the optical element 100 in accordance with the presentembodiment, the first dielectric layer 30 is formed around the firstcolumnar section 130, and the second dielectric layer 40 is formedaround the second columnar section 132. In other words, according to theoptical element 100 in accordance with the present embodiment, thedesired first dielectric layer and the second dielectric layer can bedisposed in specified regions (regions in a direction perpendicular tothe substrate 101), respectively. More specifically, the firstdielectric layer 30 can be formed in a region of the first columnarsection 130 of the surface-emitting type semiconductor laser 140. Also,the second dielectric layer 40 can be formed in a region of the secondcolumnar section 132 of the photodetector element 120.

According to the optical element 100 in accordance with the presentembodiment, the first dielectric layer 30 is formed around the firstcolumnar section 130. The first dielectric layer 30 can be readilyformed into a thick film compared to the second dielectric layer 40. Byforming the first dielectric layer 30 thick, the parasitic capacitancein the surface-emitting type semiconductor laser 140 can be reduced. Asa result, a high-speed driving of the surface-emitting typesemiconductor laser 140 becomes possible.

According to the optical element 100 in accordance with the presentembodiment, the second dielectric layer 40 is formed around the secondcolumnar section 132. The second dielectric layer 40 is easy to bemicro-processed compared to the first dielectric layer 30. By finelyprocessing the second dielectric layer 40, an electrode having a minuteand complex structure in the photodetector element 120 can be insulated.

According to the method for manufacturing the optical element 100 inaccordance with the present embodiment, the step of forming the firstdielectric layer 30 and the step of forming the second dielectric layer40 are independently conducted. For this reason, the optical element 100having the first dielectric layer 30 and the second dielectric layer 40that achieve the aforementioned actions and effects can be formed.

According to the method for manufacturing the optical element 100 inaccordance with the present embodiment, in the step for etching thefirst contact layer 111, the isolation layer 20 exists below the firstcontact layer 111, and the isolation layer 20 functions as an etchingstopper, such that the etching of the first contact layer 111 can beaccurately and readily conducted with a high precision.

According to the optical element 100 in accordance with the presentembodiment, the Al composition of the first contact layer 111 is smallerthan the Al composition of the isolation layer 20. Therefore, becausethe Al composition of the first contact layer 111 can be made smaller,ohmic contact between the first contact layer 111 and the thirdelectrode 116 can be readily obtained. As described above, the Alcomposition of the first contact layer 111 may preferably be less than0.3. Because the Al composition of the first contact layer 111 is lessthan 0.3, better ohmic contact can be obtained between the first contactlayer 111 and the third electrode 116.

According to the method for manufacturing the optical element 100 inaccordance with the present embodiment, in the step of etching theisolation layer 20, the uppermost layer 14 of the second mirror 104exists below the isolation layer 20, and the uppermost layer 14 of thesecond mirror 104 functions as an etching stopper layer, such that anupper surface of the uppermost layer 14 of the second mirror 104 is canbe accurately and readily exposed with a high precision.

According to the optical element 100 in accordance with the presentembodiment, the Al composition of the uppermost layer 14 of the secondmirror 104 is smaller than the Al composition of the isolation layer 20.Therefore, because the Al composition of the uppermost layer 14 of thesecond mirror 104 can be made smaller, ohmic contact between theuppermost layer 14 of the second mirror 104 and the second electrode 109can be readily obtained. As described above, the Al composition of theuppermost layer 14 of the second mirror 104 may preferably be less than0.3. Because the Al composition of the uppermost layer 14 of the secondmirror 104 is less than 0.3, better ohmic contact can be obtainedbetween the uppermost layer 14 of the second mirror 104 and the secondelectrode 109.

According to the optical element 100 in accordance with the presentembodiment, the Al composition of the isolation layer 20 is greater thanthe Al composition of the uppermost layer 14 of the second mirror 104,and is greater than the Al composition of the first contact layer 111.Stated otherwise, on the uppermost layer 14 of the second mirror 104 isformed the isolation layer 20 having the Al composition that is greaterthan the Al composition of the uppermost layer 14 of the second mirror104. Also, on the isolation layer 20 is formed the first contact layer111 having the Al composition that is smaller than the Al composition ofthe isolation layer 20. By laminating layers having different Alcompositions in this manner, the laminated film (the uppermost layer 14of the second mirror 104, the isolation layer 20, and the first contactlayer 111) can be used as a mirror. In other words, the isolation layer20 and the first contact layer 111 can be used as a mirror withoutadversely affecting the characteristics of the surface-emitting typesemiconductor laser 140, and the degree of freedom in device design canbe improved.

According to the optical element 100 in accordance with the presentembodiment, an optical film thickness of the isolation layer 20 is madeto be an odd multiple of λ/4, such that the isolation layer 20 canfunction as a distributed reflection type mirror. In other words, thesecond mirror 104 and the isolation layer 20 in the surface-emittingtype semiconductor laser 140 can function as a distributed reflectiontype mirror above the active layer 103. Accordingly, the isolation layer20 can function as a distributed reflection type mirror withoutadversely affecting the characteristics of the surface-emitting typesemiconductor laser 140.

According to the optical element 100 in accordance with the presentembodiment, the isolation layer 20 can be formed without being oxidized.In other words, in the oxidation step for forming the currentconstricting layer 105 in the method for manufacturing the opticalelement 100 in accordance with the present embodiment, the isolationlayer 20 can be formed without being oxidized. Because the isolationlayer 20 is not oxidized, reduction in the strength due to oxidation canbe prevented. Also, because the isolation layer 20 is not oxidized,reduction in the index of refraction due to oxidation can be prevented.As a result, the reflecting power of the isolation layer 20 whenfunctioning as a mirror can be prevented from being adversely affected.

According to the optical element 100 in accordance with the presentembodiment, because a portion of light output of the surface-emittingtype semiconductor laser 140 is monitored by the photodetector element120 and fed back to the driving circuit, output fluctuations due totemperatures or the like can be corrected, and therefore stable lightoutputs can be obtained.

Preferred embodiments of the present invention are described above, butthe present invention is not limited to them, and various modes can bemade. For example, as shown in FIG. 14, the second electrode 109 and thethird electrode 116 can be connected by using a connection electrode117. More specifically, the connection electrode 117 contacts an uppersurface of the second electrode 109, and contacts an upper surface and aside surface of the third electrode 116. As the connection electrode117, for example, gold can be used, but without being particularlylimited, a known metal, alloy, or a laminated film of them can be used.It is noted that FIG. 14 corresponds to a cross-sectional view shown inFIG. 1.

Also, in the embodiment described above, an example in which the thirdelectrode 116 is formed to cover a portion of the upper surface of thesecond electrode 109 is described. However, as shown in FIG. 15, thesecond electrode 109 can be formed to cover a portion of the uppersurface and the side surface of the third electrode 116. It is notedthat FIG. 15 corresponds to a cross-sectional view shown in FIG. 1.

Also, for example, interchanging the p-type and n-type of each of thesemiconductor layers in the above described embodiments does not deviatefrom the subject matter of the present invention. In this case, thep-type first mirror 102 and the n-type second mirror 104 of thesurface-emitting type semiconductor laser 140, and the p-type firstcontact layer 111 and the n-type second contact layer 113 of thephotodetector element 120 can form a pnpn structure as a whole. In thiscase, the materials of the second electrode 109 and the third electrode116 described above can be interchanged. In other word, morespecifically, the second electrode 109 that contacts the n-type secondmirror 104 can use a laminated film of an alloy of gold (Au) andgermanium (Ge) and gold (Au), and the third electrode 116 that contactsthe p-type first contact layer 111 can use the one including platinum(Pt).

Also, by interchanging the p-type and n-type of each of the layers ineither the surface-emitting type semiconductor laser 140 or thephotodetector element 120, the surface-emitting type semiconductor laser140 and the photodetector element 120 can have an npn structure or a pnpstructure as a whole. It is noted in this case that the second columnarsection 132 can include the first contact layer 111.

Also, in the embodiment described above, an example in which theisolation layer 20 is formed between the second mirror 104 and the firstcontact layer 111 is described. However, it is possible that theisolation layer 20 is not formed between the second mirror 104 and thefirst contact layer 111.

1. An optical element comprising: a surface-emitting type semiconductorlaser including, above a substrate, a first mirror, an active layer, asecond mirror and an isolation layer disposed on a top face of thesubstrate; a photodetector element, that is provided directly on a topsurface of the surface-emitting type semiconductor laser, including afirst contact layer in contact with the isolation layer, aphotoabsorption layer and a second contact layer; a first dielectriclayer formed above the substrate; and a second dielectric layer on a topface of the first contact layer, wherein the first dielectric layercovers a side surface of a first columnar section including at least aportion of the second mirror, the second dielectric layer covers a sidesurface of a second columnar section including at least a portion of thesecond contact layer, and the first dielectric layer, the seconddielectric layer and the isolation layer are composed in differentlayers.
 2. An optical element according to claim 1, wherein a filmthickness of the first dielectric layer is thicker than a film thicknessof the second dielectric layer.
 3. An optical element according to claim2, wherein a diameter of the second columnar section is smaller than adiameter of the first columnar section.
 4. An optical element accordingto claim 1, wherein the first dielectric layer is composed of a resin,and the second dielectric layer is composed of an inorganic dielectricsubstance.
 5. An optical element according to claim 4, wherein the resinis a polyimide resin, an acrylic resin, an epoxy resin, or a fluorineresin, and the inorganic dielectric substance is a silicon nitride or asilicon oxide.
 6. An optical element according to claim 1, wherein thesecond contact layer is disposed on the top face of the surface-emittingtype semiconductor laser, wherein the first contact layer has across-sectional surface area, parallel to the substrate layer, that islarger than cross-sectional surface areas of the photoabsorption layerand second contact layer.
 7. An optical element according to claim 1,wherein the first dielectric layer is formed on a top face of the firstmirror.